Weather has become more erratic since 1984

A study from climatologists at Princeton University suggests that weather has grown more erratic on a day-to-day
basis since the middle of the 80s.

David Medvigy, an assistant professor in the Department of
Geosciences at Princeton, and Claudie Beaulieu, a postdoctoral research fellow in Princeton's
Program in Atmospheric and Oceanic Sciences, believe that extremely
sunny or cloudy days have become more common and that swings
between stormy days and dry days have increased dramatically.

This has obviously occurred at a time when global temperatures
have been rising, but it's impossible to say for sure whether the
increase in variability is being caused by climate change. On the
one hand, a warmer world means there's more energy in the
atmosphere to generate dramatic
weather with, but on the other hand, climate is merely an
average of weather over a long period of time.

This increase in variability could have impacts on the stability
of ecosystems and on industries like agriculture, renewable energy
production and transport. "Our work adds to what we know about
climate change in the real world and places the whole problem of
climate change in a new light," saud Medvigy. "Nobody has looked
for these daily changes on a global scale. We usually think of
climate change as an increase in mean global temperature and
potentially more extreme conditions -- there's practically no
discussion of day-to-day variability."

He added: "If you don't know what role variability is playing
now, you're not in a very strong position for making remarks about
how it might change in the future," he said. "We're at a stage
where we had better take a look at what this research is pointing
out."

The most extreme variations in weather were observed in the
tropics, but those effects radiate around the glove, said William
Rossow, a professor of earth system science and environmental
engineering at the City College of New York. "Wherever it's raining
heavily, especially, or variably is where the atmosphere is being
punched. As soon as it is punched somewhere in the tropics it
starts waves that go all the way around the planet," he
said.

"Signals end up going over the whole globe, and whether they're
important in a particular place or not depends on what else is
happening," he added. "But you can think of storms as being the
disturbances in an otherwise smooth flow. That's why this is a
climate issue even though we're talking about daily variability in
specific locations."